Electrochemical copolymerization of furan and thiophene was performed at constant electrode potential in a binary solvent system consisting of boron trifluoride-ethyl ether and an additional amount of ethyl ether (mole ratio 1:2). The homopolymers and copolymers obtained were studied with in situ resonance Raman spectroscopy and in situ conductivity measurements. In situ resonance Raman spectroscopy of the copolymers shows spectroscopic properties intermediate between polyfuran and polythiophene. The conductivity of homo- and copolymer films is almost restored when the potential shift direction is reversed. The redox thermodynamics of homo- and copolymer films were also determined using the Nernst plots constructed from absorbance measurements performed in situ at various doping levels. (C) 2007 Elsevier Ltd. All rights reserved.